The invention relates to motor-fan units comprising a helicoid fan driven by an electric motor, and applies to those which are used to cool the motors of automobile vehicles. More precisely, it concerns the cooling of the electric motor.
Often this cooling cannot be ensured by the air stream created by the fan thereby posing problems. As a motter of fact, it is known that a helicoid fan has an output distinctly lower near its hub than near its periphery, which leads to the hub being given a relatively significant diameter, so that it produces a mask effect and so that the air stream circulating against or in the electric driving motor may be insufficient to cool it properly. It is particularly the case with motor-fan units used for producing or speeding up the air stream passing through the radiator for cooling the circulation water of an automobile vehicle motor, in which the electric motor driving the fan often works with a mediocre efficiency and consequently dissipates a relatively significant quantity of energy as heat.
On the other hand, when an automobile vehicle travels in fog or rain, the flow of cooling air entrains water droplets which have to be prevented from coming into contact with the electrical circuits of the motor. In addition, the fan of a cooling apparatus is placed either in front of the radiator in order to blow the air through the latter or behind in order to draw the air through it. In the first instance, the electric motor is often at the suction side of the fan while in the second instance, the motor is often at the output side. The cooling apparatus of the electric motor must therefore be installed with due regard paid to the direction of the flow, in relation to this motor, of the air stream created by the helicoid fan.
One of the aims of the invention is to allow realization of a helicoid motor-fan unit whose motor is efficiently cooled. Another aim is to ensure the cooling by air of the electric motor of a helicoid motor-fan unit, without risk of this air entraining water droplets into the electrical circuits of the motor. Yet another aim is to allow realization of a helicoid motor-fan unit whose electric motor is cooled efficiently by air without risk of water being thrown into the electrical circuits of the motor, and that the latter be placed at the output side or at the suction side of the helicoid fan.
It has been proposed to place passages in the hub or in the neighborhood of the axis of the helicoid fan to form a centrifugal or heliconcentrifugal fan driving back in the same direction as this helicoid fan. The proposal has been made to either increase the output and the output pressure in a helicoid fan, or lessen the resistance given to the outflow of an airstream by a helicoid fan when arrested or winddriven, while avoiding driving air back upstream.